Dagger is a Dependency Injection Framework for Android application. In Abusing Dependency Injection with Dagger for Dummies (in 45 minutes) we will explain from the most basic usage of Dagger to take the most of it by providing advanced tricks by using Scoped Injection.

1. ABUSING
DEPENDENCY INJECTION
WITH DAGGER
FOR DUMMIES
Saúl Díaz (@sefford)
Freakend ‘15

2. new Flipper(new Gintonic(new Gin(new Alcohol())))
FlipperGintonic GinAlcohol

3. SHOULD I USE DI WITH MY
PERSONAL/PRO PROJECT?

4. BASIC DAGGER FOR
DUMMIES

5. Flipper
Gin
Alcohol
Gintonic
Tonic
Trolling
Code
Google
Engineer
Tears
Android

6. @Module(
includes = RosieModule.class,
addsTo = {AndroidModule.class,
DrinkModule.class,
CodingModule.class
}
injects = FlipperFragment.class,
complete = true,
)
public class FlipperModule {
@Provides
@Named(“Tuenti”)
public FlipperInterface provideFlipper(Gintonic drink,
Trolling trolling, Android android) {
return new FlipperImpl(drink, trolling,
android);
}
}

7. public class FlipperFragment extends Fragment {
ObjectGraph graph;
@Inject
FlipperInterface flipper;
@Override
public void onCreate(Bundle bundle) {
graph = ObjectGraph.create(new FlipperModule());
graph.inject(this);
FlipperInterface flipper2 = graph.get(Flipper.class);
}

8. IDSPISPOPD FOR SINGLETONS
@Singleton
● By definition, Singletons cannot be tested
● Provides same instance of class for Graph
● This instance is not static

9. ADVANCED DAGGER
FOR DUMMIES

10. Lazy<Flipper> lazyFlipper;
● Creates the instance on lazyFlipper.get()
● Returns always the same instance (d’oh)
● Always done in UIThread!
LAZY INITIALIZATIONS

11. PROVIDING INSTANCES
Provider<Flipper> flipperProvider;
● Can help building your own Flipper army
● Returns a different instance each time

12. @Module(
override = true;
injects = FlipperFragment.class,
complete = true,
)
public class FlipperTestModule {
@Provides
@Singleton
public FlipperInterface provideFlipper() {
return mock(FlipperInterface.class);
}
}
MOCKING INSTANCES

13. DYNAMIC (SCOPED) INJECTION
public ObjectGraph extend() {
return graph.plus(new ExtensionModule1(),
new ExtensionModule2());
}

14. STATIC INJECTION
● Reduce boilerplate and mantenibility by
annotating classes and constructions
● Compilation-validated graph

15. SCOPED INJECTION
● Using a SOLID approach, change
implementations on runtime
● Graph runtime, validated
● Risk of “BOOOOOOM”

16. ABUSING INJECTION
FOR DUMMIES

17. CLASSIC EXAMPLE
@Module(injects = LoginActivity.class,
addsTo = AppModule.class)
// @author Antonio Leiva
public class LoginModule {
private LoginView view;
public LoginModule(LoginView view) {
this.view = view;
}
@Provides @Singleton public LoginView provideView() {
return view;
}
@Provides @Singleton
public LoginPresenter providePresenter(LoginView loginView,
LoginInteractor loginInteractor) {
return new LoginPresenterImpl(loginView, loginInteractor);
}
}

18. WHY STOPPING THERE?public class NoNfcModule() {
@Provides
public NfcInterfaceController provideNfcController() {
return new NullNfcController();
}
}
public class NfcModule() {
@Provides
public NfcInterfaceController provideNfcController(
NfcAdapter adapter) {
return new NfcController(adapter);
}
}

19. // This goes on Api15Module
@Provides
@Singleton
public StatusBarControllerInterface provideStatusBarControllerInterface() {
return new StatusBarAPI15Controller();
}
// This goes on Api19Module
@Provides
@Singleton
public StatusBarControllerInterface provideStatusBarControllerInterface() {
return new StatusBarAPI19Controller();
}
// This goes on Api21Module
@Provides
@Singleton
public StatusBarControllerInterface provideStatusBarControllerInterface() {
return new StatusBarAPI21Controller();
}

20. ONE MORE CUP OF ABUSEpublic class ActiveProfileModule() {
@Provides
public ProfilePresenterInterface provideProfilePres(...) {
return new
ActiveProfilePresenter(basePresenter,...);
}
}
public class RegularProfileModule() {
@Provides
public ProfilePresenterInterface provideProfilePres(...) {
return new
RegularProfilePresenter(basePresenter,...);
}
}

21. QUESTIONS?

22. THANKS!